The overall hypothesis of this study is: the pulse profile of insulin for old persons (60-80yrs) will be different when compared to that of young persons(20-30 yrs). The more specific hypotheses are 1)pulse profiles for young persons will have a larger pulse amplitude when compared to that of old persons; 2)pulse profiles for young and old subjects will have similar pulse frequencies; 3)interpulse insulin secretion will be elevated in older persons and 4)a significant negative correlation will exist between insulin pulse amplitude and insulin sensitivity. It is clear that hormones stimulate greater biological responses when they reach the target tissue in a pulsatile manner (the physiological manner). We will document whether part of the cause for increased insulin resistance in older persons is partially due to an altered insulin pulse profile.